Liquid crystal device, liquid crystal display panel and method for manufacturing the same

ABSTRACT

A method of manufacturing a liquid crystal panel comprises the steps of forming a gate insulating film, a channel layer and an etching stopper layer on a transparent substrate bearing a gate electrode, exposing the substrate to light from its back surface side by using the gate electrode as a light shielding mask by photolithography, developing the resist, etching the etching stopper layer, forming a source/drain layer, and etching the source/drain layer and a remaining part of the etching stopper by chemical gas phase etching.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an a-Si TFT liquid crystal device, aliquid crystal display panel and a method of manufacturing them.

2. Description of Related Art

A conventional method for manufacturing an a-Si TFT liquid crystaldisplay panel will now be described with regard to one liquid crystaldevice portion. As shown in FIGS. 15(a) and 15(b), a gate electrode 4 isfirst formed into a predetermined shape on a glass substrate 2 by ageneral technique. Then, as shown in FIG. 16, a gate insulating film 6,a channel layer 8 and a SiN_(x) film 10 serving as an etching stopperlayer are successively stacked on the entire surface of the glasssubstrate 2. As shown in FIGS. 17(a), 17(b) and 17(c), after coating aresist on the SiN_(x) film 10, the glass substrate 2 is exposed to lightfrom its back surface side by using the gate electrode 4 in thepredetermined shape as a light shielding mask, and is subsequentlysubjected to stepper exposure from its front surface side by using areticle, and then the resist is developed. Thereafter, the SiN_(x) film10 other than a portion working as an etching stopper (channelprotecting film) 14 is etched with diluted hydrofluoric acid, and thenthe resist is removed.

It is noted that the etching stopper 14 can be basically formed througha single exposing step in which the glass substrate 2 is subjected tothe stepper exposure from its front surface side by using a reticle. Inthis conventional manufacturing method, however, the etching stopper 14is formed through a two-stage exposing step: a stage of exposing thesubstrate 2 to light from its back surface side and a stage of exposingthe substrate 2 to light from its front surface side. This is because,when the etching stopper 14 is formed through a single-stage exposingstep in which the glass substrate 2 is exposed to light from its frontsurface side, the alignment with the gate electrode 4 tends to beshifted and cannot be stabilized. In contrast, if the gate electrode 4is effectively used in the two-stage exposing step, the etching stopper14 can be disposed at the center of the gate electrode 4 in aself-alignment manner. This results in providing a source electrode 26and a drain electrode 28 symmetrically about the gate electrode 4, andalso in reducing overlap areas between the gate electrode 4 and thedrain electrode 28 and between the gate electrode 4 and the sourceelectrode 26. Thus, the two-stage exposure can improve a transistorcharacteristic.

However, in manufacturing a liquid crystal display panel, there are alarge number of complicated manufacturing steps, and in addition, eachsteps requires time-consuming work. Therefore, reduction in the numberof processes not only improves the productivity but also reduces themanufacturing cost of a liquid crystal display panel in which theprocess cost accounts for a large proportion.

After being developed, the resist used for forming the etching stopper14 has a size of approximately 20×10 μm per pixel, and such rectangularresists are arranged side by side over the entire surface of an arraysubstrate. Since the area of each resist is thus small, its adhesion tothe underlying nitride film (i.e., the SiN_(x) film) is low, and hence,the resist is apt to be easily peeled off. When the resist is peeledoff, the etching stopper 14 cannot be properly formed, which leads to atransistor failure.

When the etching stopper layer 10 is etched with diluted hydrofluoricacid, the layer 10 is generally over-etched so as not to leave aninsufficiently etched portion. However, excessive over-etching makes theside surface of the etching stopper 14 be inclined inward at the footthereof, resulting in the formation of a “concave” 15, which is hiddenin a top view as shown in FIG. 17(c). When films and/or foreign matterto be deposited in subsequent steps are attached to the concave 15, theycannot be removed through cleaning and etching. As a result, as shown inFIG. 18, a leakage current flows between the source electrode 26 and thedrain electrode 28 formed on the etching stopper 14, which leads to aleakage failure of the transistor.

SUMMARY OF THE INVENTION

As the result of researches to remove the above disadvantages, thepresent inventors have eventually found the present invention. An objectof the present invention is to reduce the number of steps, especiallythe number of exposing steps in manufacture of a liquid crystal device,so as to improve the productivity and reduce the manufacturing cost.

Another object of the present invention is to prevent a failure of atransistor related to an etching stopper portion, so as to improve theyield and the quality of a liquid crystal display panel.

The liquid crystal device of the present invention comprises an etchingstopper whose two pairs of opposite side surfaces are inclined atdifferent angles. Specifically, the two pairs of opposite side surfacesof the etching stopper of the liquid crystal device are respectivelyetched in different steps, and hence, they are generally inclined atdifferent angles.

Alternatively, the liquid crystal device of the present inventioncomprises an etching stopper, one of opposite side surfaces of which isat substantially right angles to the substrate or tapers away from thesubstrate. When a side surface extending along current flow isoppositely tapered, a leakage current can be caused owing to a remainingimpurity and the like. Therefore, such a side surface is desired to beat right angles or normally tapered. On the other hand, when a sidesurface extending perpendicularly to the current flow (namely, a sidesurface covered with a source electrode and a drain electrode) isoppositely tapered and is not controlled, the overlap area between thegate electrode and the source (or drain) electrode can be varied,resulting in varying the parasitic capacitance of each device.Accordingly, such a side surface is preferably controlled to be at rightangles or to be normally tapered. The side surface extendingperpendicularly to the current flow can be also formed into a normallytapered shape through wet etching in the present invention because thecovering area of the etching stopper can be large so as to reduce theover-etching amount attained when the etching is almost completed.

In the liquid crystal device of the present invention, at least one sidesurface of an etching stopper extending perpendicularly to current flow,namely, at least one side surface not covered with the source electrodeor the drain electrode, is at substantially right angles to thesubstrate or tapers away from the substrate. Accordingly, no attachmentsuch as an insufficiently etched film and an impurity remains on theetching stopper portion, resulting in preventing a leakage current fromflowing between the source electrode and the drain electrode.

Alternatively, the method of manufacturing a liquid crystal displaypanel of the present invention comprises at least a step ofsimultaneously etching an etching stopper and a source/drain layer. Thismanufacturing method makes it possible to eliminate a concave of theetching stopper, which is formed in the channel width direction as aresult of excessive over-etching, and hence, a leakage current can beprevented from flowing between the source electrode and the drainelectrode.

Moreover, in the alternative method of manufacturing a liquid crystaldisplay panel according to the present invention, a gate insulatingfilm, a channel layer and an etching stopper layer are formed on atransparent substrate bearing a gate electrode, and the substrate isexposed to light from its back surface side by using the gate electrodeas a light shielding mask by a photography technique. Then, the resistis developed, and the etching stopper layer is etched, and thereby anetching stopper is formed. This manufacturing method makes it possibleto form the etching stopper through an only sigle-stage exposing step.As a result, the productivity can be largely improved, and theoccurrence of formation failures of the etching stopper derived from aresist failure can be substantially avoided.

Moreover, in the method of manufacturing a liquid crystal display panel,after the aforementioned steps, a source/drain layer is formed. Then,the source/drain layer and a remaining portion of the etching stopperare etched through chemical gas phase etching by photolithography. Thismanufacturing method makes it possible to eliminate a concave of theetching stopper, which is formed in the channel width direction as aresult of excessive over-etching, and therefore, a leakage current canbe prevented from flowing between the source electrode and the drainelectrode.

In the liquid crystal device, the liquid crystal display panel and themethod for manufacturing them according to the present invention,exposure of an etching stopper layer includes merely one exposureprocess using a gate electrode as a light shielding mask. Thus, thenumber of exposure processes in this invention is smaller by one thanthat of the conventional technique. Since the method of the presentinvention does not include the exposure process using a light-shieldingmask such as a reticle, which requires preciseness in alignment andtakes a long time, the productivity can be remarkably improved.

In addition, a resist for forming the etching stopper is formed on theentire gate electrode and has a larger adhesion area than that used inthe conventional technique. Therefore, the photoresist is less likely topeel off, and hence, the occurrence of formation failures of the resistcan be suppressed, and the failure of transistors can be reduced.Furthermore, the manufacturing cost can be largely decreased because anexpensive reticle is not necessary.

In the manufacturing method of the present invention, an etching stopperwhich is longer in the channel width direction than the width of asource/drain electrode under layer is formed through an exposure processfrom the back surface side of a substrate and an exposure process fromthe front surface thereof. Therefore, a reticle and anotherlight-shielding mask used in the exposure process from the front surfaceof the substrate can be merely roughly aligned. As a result, not onlythe workability involved in the alignment can be remarkably improved butalso the occurrence of failures can be largely reduced and the devicequality can be stabilized.

Furthermore, the etching stopper longer in the channel width directionthan the width of the source/drain electrode under layer is removed atits ends through etching simultaneously with the formation of thesource/drain electrode under layer. Therefore, a resist used for formingthe source/drain electrode under layer can be very easily aligned, andthe occurrence of failures involved in the alignment can besubstantially avoided.

Moreover, since the etching stopper longer in the channel widthdirection is etched at its ends simultaneously with the formation of thesource/drain electrode under layer, even when over-etching in theetching of the etching stopper layer is so excessive that a concave inan oppositely tapered shape is formed, the concave extending over asource electrode and a drain electrode can be removed through etching.As a result, no leakage current flows between the source electrode andthe drain electrode, and the performance and the quantity can beimproved. In addition, since the concave formed through the excessiveover-etching can be thus removed, resultant products can be used as goodproducts. Thus, the occurrence of failure can be largely reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are an enlarged plan view and an enlarged sectionalview, respectively, showing a procedure for forming a gate electrode inthe manufacture of a liquid crystal device and a liquid crystal displaypanel according to the present invention;

FIG. 2 is an enlarged sectional view showing a procedure for forming agate insulating film, a channel layer and an etching stopper layer;

FIGS. 3(a) and 3(b) are an enlarged plan view and an enlarged sectionalview, respectively, showing a procedure for forming an etching stopper;

FIG. 4 is an enlarged sectional view showing a procedure for forming asource/drain layer;

FIGS. 5(a), 5(b) and 5(c) are explanatory views illustrating a procedurefor processing the source/drain layer, and FIG. 5(a) is an enlarged planview, FIG. 5(b) is an enlarged sectional view and FIG. 5(c) is anenlarged sectional view taken on line I—I of FIG. 5(b);

FIG. 6 is an enlarged perspective view showing a liquid crystal deviceportion of FIGS. 5(a) to 5(c);

FIGS. 7(a) and 7(b) are an enlarged plan view and an enlarged sectionalview, respectively, showing a procedure for forming a transparentconductive film;

FIG. 8 is an enlarged sectional view showing a procedure for forming athrough hole:

FIGS. 9(a) and 9(b) are an enlarged plan view and an enlarged sectionalview, respectively, showing a procedure for forming a signal line;

FIG. 10 is an enlarged perspective view of the liquid crystal deviceportion of FIGS. 9(a) and 9(b);

FIG. 11 is an enlarged sectional view of the liquid crystal device andthe liquid crystal display panel manufactured by forming a surfaceprotecting layer;

FIGS. 12(a) and 12(b) are an enlarged plan view and an enlargedsectional view, respectively, showing a procedure for forming an etchingstopper in another manufacturing method for a liquid crystal device anda liquid crystal display panel according to the present invention;

FIG. 13 is an enlarged sectional view showing a procedure for forming asource/drain layer;

FIGS. 14(a) to 14(d) are explanatory views illustrating a procedure forprocessing the source/drain layer, and FIG. 14(a) is an enlarged planview, FIG. 14(b) is an enlarged sectional view, FIG. 14(c) is anenlarged sectional view taken on line II—II of FIG. 14(b), and FIG.14(d) is a sectional view taken on line III—III of FIG. 14(a);

FIGS. 15(a) and 15(b) are an enlarged plan view and an enlargedsectional view, respectively, showing a procedure for forming a gateelectrode in a conventional method of manufacturing a liquid crystaldevice and a liquid crystal display panel;

FIG. 16 is an enlarged sectional view showing a procedure for forming agate insulating film, a channel layer and an etching stopper layer inthe conventional method;

FIGS. 17(a) to 17(c) are explanatory views illustrating a procedure forforming an etching stopper in the conventional method, and FIG. 17(a) isan enlarged plan view, FIG. 17(b) is an enlarged sectional view and FIG.17(c) is an enlarged perspective view of the resultant etching stopper;and

FIG. 18 is an enlarged perspective view of a liquid crystal deviceportion in a liquid crystal device and a liquid crystal display panelmanufactured by the conventional method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a preferred embodiment of a liquid crystal device, a liquid crystaldisplay panel and a method of manufacturing the device and the displaypanel will be described with reference to the accompanying drawings. Itis noted that only a portion corresponding to one pixel is shown in thedrawings for simplification. In addition, the sectional viewsillustrate, in principle, a TFT portion, a storage capacitance portionCs and a pad portion for simplifying the description.

As shown in FIGS. 1(a) and 1(b), a gate electrode 4 is first formed on atransparent substrate 2. The most preferable transparent substrate 2 isa glass substrate, but can be a resin substrate or a flexible substrateas far as it is transparent and, in particular, good at heat resistance.

The gate electrode 4 consists of one or more layers of at least oneelement selected from the group consisting of MoW, Cr, Cu, Ni, Al, Mo,Ag and the like. Preferably, the gate electrode 4 has not only excellentconductivity but also excellent adhesion to the transparent substrate 2,and more preferably, has such a property that atoms and molecules of theelectrode material are not diffused into a gate insulating film 6 to beformed thereon. Also, the gate electrode 4 is formed on the entiresurface of the transparent substrate 2 by evaporating a specified metalor by adhering a metal foil. Thereafter, the resultant substrate 2 iscoated with a photoresist, and subsequently subjected to stepperexposure by using a reticle. Then, the resist is developed.Subsequently, after the metal layer other than a portion working as thegate electrode 4 is removed through plasma etching, the photoresist isremoved. Thus, the gate electrode 4 is formed.

Next, as shown in FIG. 2, the gate insulating film 6, a channel layer 8and an etching stopper layer 10 are successively formed in that order onthe entire transparent substrate 2 bearing the gate electrode 4. Thegate insulating film 6 is preferably formed from one or more layers ofone or more materials. In particular, SiO_(x) and SiN_(x) are preferablyused as the material for the gate insulating film 6, and morepreferably, a SiO_(x) film 6 a is formed on the transparent substrate 2side and a SiN_(x) film 6 b is formed on the SiO_(x) film 6 a. Theformation of the SiN_(x) film 6 b is preferable to improve adhesion tothe channel layer 8 which is to be formed thereon.

Furthermore, amorphous silicon (a-Si) is used as the material for thechannel layer 8, and SiN_(x) is used as the material for the etchingstopper layer 10 which is to be formed thereon. All these layers areformed by a general technique.

Then, as shown in FIGS. 3(a) and 3(b), after the photoresist (not shown)is applied to the etching stopper layer 10, the transparent substrate 2is exposed to light by using the gate electrode 4 as a light shieldingmask from its back surface side, that is, the surface side not bearingthe etching stopper layer 10 and the like. Subsequently, the transparentsubstrate 2 is exposed to light from its front surface side, which isnot affected by the gate electrode 4, by using a light shielding mask.When a reticle is used as the light shielding mask, stepper exposure isadopted. When a light shielding mask including a photomask covering theentire substrate 2 is used, the exposure is carried out once. Any of thereticle and other light shielding masks used in the light exposure fromthe front surface side of the substrate 2 includes a masking portionwhich is longer than at least the width (along the channel widthdirection) of a source/drain electrode under layer 12 to be formed in asubsequent step. Accordingly, when the photoresist is developed, areasof photoresist, which is not exposed to light in neither the exposurefrom the back surface side of the substrate 2 nor the exposure from thefront surface side thereof. Therefore, when the etching stopper layer 10alone is wet etched, an etching stopper 14, which is longer in thechannel width direction than the source/drain electrode under layer 12is formed as shown in FIG. 3(a). Thereafter, the photoresist is removedfrom the etching stopper 14. In these exposing steps, the reticle andother shielding masks used in the exposure on the front surface of thesubstrate 2 can be roughly aligned. As a result, the workabilityinvolved in the alignment can be remarkably improved as well as theoccurrence of failure can be largely reduced, and hence, the devicequality can be stabilized.

Next, as shown in FIG. 4, a source/drain layer 16 is formed on thetransparent substrate 2 bearing the etching stopper 14. As the materialfor the source/drain layer 16, n⁺ type a-Si is generally used forattaining ohmic contact with a source electrode and a drain electrode tobe formed thereon.

After forming the source/drain layer 16, a photoresist is applied to theresultant substrate 2. Then, as shown in FIGS. 5(a) to 5(c), theresultant substrate 2 is subjected to stepper exposure by using areticle having a mask in substantially the same shape as a signal lineincluding the source/drain electrode under layer 12, and plasma etchingis then carried out. Through the plasma etching, the source/drain layer16, the etching stopper 14, the channel layer 8 and the SiN_(x) film 6 bof the gate insulating film 6 are simultaneously etched intosubstantially the same shape as the signal line. At this time, as shownwith dashed lines in FIG. 6, the both ends in the channel widthdirection of the etching stopper 14 are removed through the etching. Asa result of this plasma etching, the source/drain electrode under layer12, the etching stopper 14, the channel layer 8 and the SiN_(x) film 6 bare formed at substantially right angles to the transparent substrate 2or they are tapered in that order. Thus, the angles of the tilts of theboth side surfaces of the etching stopper 14 are generally different.

Thereafter, as shown in FIGS. 7(a) and 7(b), a transparent conductivefilm (not shown) of ITO or the like working as a pixel electrode layeris formed on the entire surface of the substrate 2. Then, pixelelectrode layers 18 having a predetermined shape are formed by a generalmethod comprising the steps of coating of photoresist, stepper exposure,development of the photoresist, and wet etching, and then photoresist isremoved. Furthermore, coating of a photoresist, stepper exposure,development of the photoresist and wet etching are successively carriedout in the same manner as the above, so that a through hole 22 can beformed in the gate insulating film 6 covering the gate electrode 4corresponding to a pad portion 20 as shown in FIG. 8. After forming thethrough hole 22, the photoresist is removed.

Then, as shown in FIGS. 9(a) and 9(b), conductive metal (not shown) isdeposited to form the signal line 24, the source electrode 26, the drainelectrode 28 and an electrode contact portion 30. The conductive metalconsists of one or more layers of one or more metals having goodconductivity. The conductive metal is preferably a lamination includinga Mo layer, an Al layer and another Mo layer, but it is not limited bythe above. After forming one or more layers of the conductive metal byevaporation or the like, the steps of coating of a resist, stepperexposure and development of the resist are successively carried out inthe same manner as the above. Then, the conductive metal is etched by awet etching method to form the signal line 24, the source electrode 26,the drain electrode 28 and the electrode contact portion 30. Thereafter,the source/drain electrode under layer 12 exposed between the sourceelectrode 26 and the drain electrode 28 and the like is etched by plasmaetching. In this plasma etching, the source/drain electrode under layer12 of n⁺ type a-Si is etched as shown in FIG. 10, however, the etchingstopper 14 of SIN_(x) remains, and hence, the channel layer 8 can beprevented from being etched.

Next, as shown in FIG. 11, a surface protecting layer 32 is formed asnecessary. The surface protecting layer 32 is made from a materialhaving a high electric insulating property, such as SiN_(x). Afterdepositing such an insulating material by a general technique, aphotoresist is coated, stepper exposure is conducted, the photoresist isdeveloped, plasma etching is conducted, and the photoresist is removed.In this manner, a liquid crystal device and a liquid crystal displaypanel 34 covered with the surface protecting layer 32 excluding a partof electrodes and the like can be manufactured.

In the aforementioned manufacturing method, the etching stopper 14,which are longer in the channel width direction than the width of thesource/drain electrode under layer 12, are formed through the exposingstep from its back surface side and the exposing step form its frontsurface side as described with reference to FIGS. 3(a) and 3(b).Accordingly, the reticle and other light shielding masks used in theexposing step from the front surface side of the substrate 2 can beroughly aligned. As a result, the workability involved in the alignmentcan be remarkably improved, the occurrence of failures can be largelyreduced, and the device quality can be stabilized.

Moreover, as described with reference to FIGS. 5(a) to 5(c), both endportions of the etching stopper 14, which are longer in the channelwidth direction than the width of the source/drain electrode under layer12, are removed through the etching cocurrently with the formation ofthe source/drain electrode under layer 12. Accordingly, the resist usedfor forming the source/drain electrode under layer 12 can be very easilyaligned, and the occurrence of failures involved in the alignment can bealmost eliminated.

Furthermore, both end portions of the etching stopper 14, which arelonger in the channel width direction, are removed through the etchingcocurrently with the formation of the source/drain electrode under layer12 as described with reference to FIGS. 5(a) to 5(c) and FIG. 6.Accordingly, in etching step of etching stepper layer 10, as shown inFIG. 6, even when excessive over-etching produces a concave 15 in theshape of opposite taper, the concave 15 spreading over the sourceelectrode 26 and the drain electrode 28 can be removed by being etchedas shown in FIG. 6. As the result, since no leakage occurs between thesource electrode 26 and the drain electrode 28, the performance and thequality of the resultant device can be improved. Moreover, theoccurrence of failure can be significantly reduced.

One embodiment of the liquid crystal device, the liquid crystal displaypanel and the method for manufacturing them according to the presentinvention has thus been described, but the present invention is notlimited to the aforementioned embodiment. Now, another embodiment willbe described, in which like reference numerals are used to refer to likeelements in drawings and the description of the elements is partlyomitted.

For example, a gate electrode 4 is first formed on a transparentsubstrate 2 as shown in FIGS. 1(a) and 1(b) as in the aforementionedembodiment. Then, as shown in FIG. 2, a gate insulating film 6, achannel layer 8 and an etching stopper layer 10 are successively formedon the entire surface of the transparent substrate 2 bearing the gateelectrode 4.

Subsequently, the resultant transparent substrate 2 is coated with aphotoresist (not shown) and is exposed to light from its back surface,namely, the surface not bearing the etching stopper layer 10 and thelike, by using the gate electrode 4 as a light shielding mask as shownin FIGS. 12(a) and 12(b). The photoresist is then immediately developed,and wet etching is conducted for removing the photoresist. Through thisetching, an etching stopper 36 in substantially the same shape as thegate electrode 4 is formed. Thereafter, a source/drain layer 16 isformed on the transparent substrate 2 bearing the etching stopper 36 asshown in FIG. 13.

Next, the resultant transparent substrate 2 is coated with aphotoresist. The substrate 2 is then subjected to stepper exposure usinga reticle having a masking portion in substantially the same shape as asignal line including a source/drain electrode under layer 12 as shownin FIGS. 14(a) through 14(d), and plasma etching is carried out. Throughthis plasma etching, the source/drain layer 16, the etching stopper 36,the channel layer 8 and a SiN_(x) film 6 b of the gate insulating film 6are simultaneously etched into substantially the same shape as thesignal line (i.e., the shape of the resist for the source/drain layer16). At this point, the ends in the channel width direction of theetching stopper 36 are removed through the etching. Also through thisplasma etching, the source/drain electrode under layer 12, the etchingstopper 36, the channel layer 8 and the SiN_(x) film 6 b are made tohave side surfaces substantially at right angles to the transparentsubstrate 2. At the same time, an interlayer insulating film at acrossing point 38 between the signal line (12) and the gate electrode 4is formed in a stacked layer structure including the gate insulatingfilm 6 (of the films 6 a and 6 b), the channel layer 8 and the etchingstopper layer 10 (i.e., the etching stopper 36).

Thereafter, a transparent conductive film such as ITO serving as a pixelelectrode layer is formed on the entire surface of the substrate 2 inthe same manner as in the aforementioned embodiment, thereby similarlyforming a pixel electrode 18 in a desired shape (See FIGS. 7(a) and7(b)). Then, a through hole 22 is formed in the gate insulating film 6covering the gate electrode 4 corresponding to a pad portion 20 (SeeFIG. 8). Subsequently, a signal line 24, a source electrode 26, a drainelectrode 28 and an electrode contact portion 30 are formed (See FIGS.9(a) and 9(b)). Then, a surface protecting layer 32 is formed, ifnecessary. Thus, a liquid crystal device and a liquid crystal displaypanel 34 are manufactured.

This manufacturing method for a liquid crystal device and a liquidcrystal display panel can attain all the effects attained by theaforementioned embodiment. Additionally, in this manufacturing method,the exposure process for forming the etching stopper layer includesmerely the exposure using the gate electrode as a light shielding mask,and hence, the number of exposure processes is reduced by one ascompared with that in the aforementioned manufacturing method. Theexposure process using a light shielding mask such as a reticle requiresvery high preciseness in the alignment of the light shielding mask andtakes a long period of time. Therefore, reduction in the number of suchprocesses can largely improve the productivity.

In addition, the resist for forming the etching stopper is formed on theentire gate electrode and has a larger adhesion area than that used inthe conventional technique. Therefore, the photoresist can be lesslikely to peel off. In the conventional technique, a photoresist usedfor forming an etching stopper has a small area and tends to peel off.In contrast, since the photoresist is formed on the entire gateelectrode in this method as described above, the occurrence of formationfailures of the photoresist is suppressed, resulting in reducing thefailure of transistors. Moreover, the manufacturing cost can be largelyreduced because an expensive reticle is not necessary.

The liquid crystal device, the liquid crystal display panel and themethod for manufacturing them according to the present invention havethus been described, however, the present invention can be materializedin the other embodiments.

Specifically, according to the manufacturing method of the presentinvention, the opposite two side surfaces of an etching stopper of a TFTliquid crystal device are generally formed at substantially right anglesto the substrate as described above. However, depending upon adjustmentin the alignment of a light shielding mask and the like, the effect ofthe present invention can be attained as far as at least one of the sidesurfaces is substantially at right angles to the substrate.

Furthermore, a usable resist is not limited to a wet-type resist, butcan be a film-like resist for thermo-compression bonding. When theresist is of the wet type, the resist is formed by coating or spraying.Moreover, the resist can be either negative or positive. However, theshape of a light shielding mask is inverted in accordance with the typeof the resist.

Furthermore, the etching method can be wet etching or dry etchingselected appropriately in accordance with the material to be etched. Thedry etching is not limited to plasma etching but can be any otheretching method including such as chemical gas phase etching such asreactive ion etching, ion beam etching and reactive ion beam etching.

Also, the light shielding mask can be a mask formed for one exposure ora reticle-type mask which is used in repeated exposure (stepperexposure) with the mask properly moved. The light shielding mask isproperly selected in consideration of the productivity and themanufacturing cost.

Moreover, the effect of the present invention can be attained byconducting a process for simultaneously etching the source/drainelectrode under layer 12 and the etching stopper 14 in addition to theprocesses of the conventional method. In this manner, a leakage currentbetween the source electrode 26 and the drain electrode 28 can beprevented, although the processes are more complicated.

In addition, the shape of a transparent substrate is not necessarilyplane but can be curved. Thus, various changes, modifications, andimprovements can be made to the embodiments on the basis of knowledge ofthose skilled in the art without departing from the scope and spirit ofthe present invention.

What is claimed is:
 1. A method of manufacturing a liquid crystaldisplay panel which includes a thin film transistor having a channellayer, an etching stopper disposed on the channel layer, and source anddrain layers electrically contacting with and disposed on the channellayer, comprising the steps of: providing the etching stopper on thechannel layer, the etching stopper having ends and a length in a channelwidth direction; providing a source/drain layer on the channel layer andthe etching stopper, the source/drain layer having a width in thechannel width direction, wherein the length of the etching stopper islonger in the channel width direction than the width of the source/drainlayer; simultaneously etching at least the etching stopper and thesource/drain layer to form the source and drain layers; and removing theends of the etching stopper.
 2. A method of manufacturing a liquidcrystal display panel comprising the steps of: forming a gate electrodeon a transparent substrate; forming a gate insulating film on an entiresurface of the substrate; forming a channel layer on the gate insulatingfilm; forming an etching stopper layer on the channel layer, the etchingstopper layer having ends and a length in a channel width direction;forming a resist film on the etching stopper layer; exposing thesubstrate to light from its back surface by using the gate electrode asa shielding mask; developing the resist film; etching the etchingstopper layer; removing the resist film; forming a source/drain layer onthe entire surface of the substrate, the source/drain layer having awidth in the channel width direction, wherein the length of the etchingstopper layer is longer in the channel width direction than the width ofthe source/drain layer; forming a resist layer on the source/drainlayer; exposing the substrate to light; developing the resist layer;simultaneously etching the source/drain layer and a remaining portion ofthe etching stopper layer; removing the ends of the etching stopperlayer; and removing the resist layer.
 3. The method for manufacturing aliquid crystal display panel according to claim 2, wherein the step ofetching the etching stopper layer is the step of wet-etching the etchingstopper layer by using diluted hydrofluoric acid.
 4. The method ofmanufacturing a liquid crystal display panel according to claim 2,wherein the simultaneously etching step is performed through chemicalgas etching.
 5. The method for manufacturing a liquid crystal displaypanel according to claim 4, wherein the source/drain layer is made froman n⁺ type a-Si layer.
 6. The method for manufacturing a liquid crystaldisplay panel according to claim 4, wherein the step of exposing thesubstrate to light is the step of conducting stepper exposure by using areticle.
 7. The method of manufacturing a liquid crystal display panelaccording to claim 4, further comprising, after the step of removing theresist layer, the steps of: forming a transport electrode; and forming asignal line.
 8. The method for manufacturing a liquid crystal displaypanel according to claim 7, wherein the signal line is made particularlyfrom a lamination consisting of a Mo layer, an Al layer and another Molayer.